Dependence of superconducting layer thickness on critical current density of YBCO-coated conductors at high temperatures

摘要

The critical current properties were investigated in the superconducting layer thickness range of 0.5–1.5 μm for PLD processed YBCO coated tapes deposited on IBAD substrates. The measurements were done in low and high electric field regions around the order of 10−8 V/m and 10−4 V/m, respectively. As a result, it was found that the critical current density Jc decreased with increasing thickness in both measurements at low magnetic fields. However, the thickness dependence of the irreversibility field Bi were different between the two measurements: Bi increased with decreasing thickness in the high electric field region, while Bi decreased with decreasing thickness in the low electric field region. The n value increased monotonically with increasing thickness. The observed results were approximately explained by the irreversible thermodynamic principle that the transverse flux bundle size is determined so that the critical current density is maximized.